Thermoplastic polymer compositions or alloys made by blending together polycarbonate polymer and ABS polymer (PC/ABS) are materials of industrial importance. In order to flame retard such compositions, a number of stringent requirements must be satisfied. Besides being halogen-free and suitably effect in retarding flame, the flame retardant should have a high heat distortion temperature, and a high softening temperature. Thus, even in the absence of an anti-dripping agent such as a Teflon(copyright) polymer, the flame retardant should exhibit at least a V-2 rating when test samples are subjected to the UL-94 test procedure. The flame retardant itself should be thermally stable at temperatures of at least about 260xc2x0 C. and preferably above 260xc2x0 C., and should not contribute materially to discoloration of the finished polymer composition, especially during exposure to molding or extrusion temperatures. In addition, the flame retardant should not be prohibitively expensive to produce.
In an attempt to provide flame retardants satisfying these requirements, many different phosphorus additives were synthesized and evaluated. Many of the samples failed to meet the thermal stability requirement or decomposed on processing with the PC/ABS.
Pursuant to this invention certain halogen-free phosphoramidate compounds have been found to satisfy the foregoing requirements. The phosphoramidates used pursuant to this invention are of three types, namely, (I) O,O-diaryl-N-arylphosphoramidates, (II) arylene-N,Nxe2x80x2-bis(O,O-diarylphosphoramidates) in which the nitrogen atoms are in the 1,3 or 1,4 positions on an arylene ring, and (III) N,Nxe2x80x2-piperazinediylbis(O,O-diarylphosphoramidates).
Thus this invention provides in one of its embodiments a flame retardant polymer composition which comprises a blend made from (i) a polycarbonate-ABS polymer composition, and a flame retardant amount of (ii) at least one halogen-free phosphoramidate selected from (I) O,O-diaryl-N-arylphosphoramidates, (II) arylene-N,Nxe2x80x2-bis(O,O-diarylphosphoramidates) in which the nitrogen atoms are in the 1,3 or 1,4 positions on an arylene ring, and (III) N,Nxe2x80x2-piperazinediylbis(O,O-diarylphosphoramidates).
Another embodiment is the method of rendering a PC/ABS polymer composition flame retardant which comprises blending with such composition a flame retardant amount of at least one halogen-free phosphoramidate flame retardant selected from (I) O,O-diaryl-N-arylphosphoramidates, (II) arylene-N,Nxe2x80x2-bis(O,O-diarylphosphoramidates) in which the nitrogen atoms are in the 1,3 or 1,4 positions on an arylene ring, and (III) N,Nxe2x80x2-piperazinediylbis(O,O-diarylphosphoramidates).
The above phosphoramidates can be depicted by the following formulas:
(RO)2P(O)(NHR)xe2x80x83xe2x80x83(I)
[(RO)2P(O)NHxe2x80x94]2Arxe2x80x83xe2x80x83(II)
[(RO)2P(O)xe2x80x94]2Zxe2x80x83xe2x80x83(III)
where each R is the same or different and is an aryl group, Ar is an arylene group that is bonded in its 1,3- or 1,4-positions to the respective depicted nitrogen atoms, and Z is the piperazinediyl group. Each R group typically contains in the range of 6 to about 18 carbon atoms, examples of which include phenyl, tolyl, ethylphenyl, xylyl, mesityl, biphenylyl, naphthyl, methylnaphthyl, 4-dimethylaminophenyl, and 4-methoxyphenyl. Preferably each R is a hydrocarbyl aryl group (i.e., it consists of carbon and hydrogen atoms), and preferably each R is a monocyclic aryl group having in the range of 6 to 14, and more preferably in the range of 6 to 10 carbon atoms. Most preferably each R group is phenyl.
The flame retardants of this invention are effective in the absence of flame retardant auxiliaries such as (1) antimony-based synergists, (2) halogen-containing flame retardants, and (3) sulfur or sulfur-containing flame retardant auxiliaries. Indeed, it is preferred to use the phosphoramidates of this invention in the absence of any of these three types of flame retardant auxiliary additives.
In one of its embodiments this invention a flame retardant polymer composition which comprises a blend made from PC/ABS, and a flame retardant amount in the range of about 5 to about 30 wt % (preferably in the range of about 10 to about 20 wt %) of at least one halogen-free phosphoramidate described above. Unless otherwise specified, all weight percentages of phosphoramidate given in this document are based on the total weight of the substrate polymer plus phosphoramidate.
In another embodiment, the above PC/ABS substrate polymer and phosphoramidate flame retardant are in the form of a powder blend or master batch wherein the composition contains a higher concentration of the phosphoramidate than the particular concentration to be used in the finished polymer composition. Thus such powder blend or master batch can contain up to about 99 wt % of the phosphoramidate, but normally will contain in the range of about 20 to about 60 wt % phosphoramidate. Such compositions are mixed with additional substrate polymer when producing the molded or extruded article or shape.
In connection with blends that are or are to be molded or extruded (i.e., expressed through a die) without further dilution with substrate polymer, the term xe2x80x9cflame retardant amountxe2x80x9d as used herein, including the claims hereof, means that the amount of phosphoramidate used in forming the composition is at least the minimum amount in the range of about 5 to about 30 wt % needed with the particular substrate polymer with which the phosphoramidate is blended to enable molded test specimens made from the resultant blend to exhibit at least a V-2 rating in the UL-94 test procedure. More than such minimum amount of phosphoramidate relative to the amount of polymer can be used in these situations and be considered a flame retardant amount, provided that the weight ratio of phosphoramidate to polymer is in the range of about 5 to about 30 wt %. On the other hand, in connection with master batch blends or powder preblends that are prepared for future dilution with additional substrate polymer preparatory to making finished molded, extruded or foamed shapes or objects (articles), any amount of phosphoramidate that is above the minimum xe2x80x9cflame retardant amountxe2x80x9d can be used.
Other embodiments of the invention will be still further apparent from the ensuing description and the appended claims.
The phosphoramidates used in the practice of this invention are composed of three groups. One group is composed of O,O-diaryl-N-arylphosphoramidates, compounds of the above formula (I).
The second and third groups are depicted by formulas (II) and (III), respectively. While the aryl groups of all three such groups are most preferably unsubstituted phenyl groups, one or more of them can be substituted with up to 5 hydrocarbyl substituents, e.g., alkyl, alkenyl, cycloalkyl, cycloalkenyl, cycloalkylalkyl, aryl, aralkyl, or one or more non-halogen containing functional substituents such as alkoxy, dialkylamino, nitro, cyano, carboxylic, esterified carboxylic, or like innocuous substituent, or a combination of hydrocarbyl and such functional substituent(s). A few non-limiting examples of formula (I) phosphoramidates include ditolyl-N-phenylphosphoramidate, ditolyl-N-tolylphosphoramidate, diphenyl-N-xylylphosphoramidate, di(ethylphenyl)-N-(p-propylphenyl)phosphoramidate, diphenyl-N-(2,4,6-trimethylphenyl)phosphoramidate, diphenyl-N-(m-nitrophenyl)phosphoramidate, and diphenyl-N-(p-biphenylyl)phosphoramidate. Of the formula (I) phosphoramidates, diphenyl-N-phenylphosphoramidate is most preferred.
The arylene group of the Group II phosphoramidates can be a phenylene, naphthalene, dihydronaphthalene, or tetrahydronaphthalene group in which the univalent bonds to the respective nitrogen atoms are in the 1,3- or 1,4-positions of the phenylene group of such arylene groups. The arylene group can be unsubstituted or substituted with hydrocarbyl substituents, e.g., alkyl, alkenyl, cycloalkyl, cycloalkenyl, cycloalkylalkyl, aryl, aralkyl, and/or one or more non-halogen containing functional substituents such as alkoxy, dialkylamino, nitro, cyano, carboxylic, esterified carboxylic, or like innocuous substituent(s). In any case, the arylene group will typically contain in the range of 6 to about 18 carbon atoms, and preferably in the range of 6 to about 12 carbon atoms. More preferably the arylene group is 1,4-phenylene, and most preferably it is 1,3-phenylene. A few non-limiting examples of formula (II) phosphoramidates include 1,4-phenylene-N,Nxe2x80x2-bis(O,O-diphenylphosphoramidate), 1,3-phenylene-N,Nxe2x80x2-bis(O,O-ditolylphosphoramidate), 1,4-phenylene-N,Nxe2x80x2-bis(O,O-di-p-tert-butylphenylphosphoramidate), 1,3 -phenylene-N,Nxe2x80x2-bis(O,O-di-p-anisylphosphoramidate), 1,4-phenylene-N,Nxe2x80x2-bis(O,O-dimesitylphosphoramidate), and 1,4-naphthalene-N,Nxe2x80x2-bis(O,O-diphenylphosphoramidate). Of the formula (II) phosphoramidates, 1,3-phenylene-N,Nxe2x80x2-bis(O,O-diphenylphosphoramidate) is most preferred.
A few non-limiting examples of N,Nxe2x80x2-piperazinediylbis(O,O-diarylphosphoramidates) of formula (III) include such compounds as N,Nxe2x80x2-piperazinediylbis(O,O-ditolylphosphoramidate), N,Nxe2x80x2-piperazinediylbis(O,O-dixylylphosphoramidate), N,Nxe2x80x2-piperazinediylbis(O,O-dimesitylphosphoramidate), N,Nxe2x80x2-piperazinediylbis[O,O-di(ethylphenyl)phosphoramidate], and N,Nxe2x80x2-piperazinediylbis(O,O-di-p-anisylphosphoramidate). N,Nxe2x80x2-piperazinediylbis(O,O-diphenylphosphoramidate) is the most preferred phosphoramidate of formula (III).
Methods which can be used or adapted for use in preparing such compounds are known and reported in the literature. Especially desirable processes for the synthesis of the phosphoramidates used in the practice of this invention are illustrated in the Examples hereinafter.
As is known in the art, PC/ABS polymers are typically comprised of from about 50 to about 90 wt % of a polycarbonate resin and from about 10 to about 50 wt % of an acrylonitrile-butadiene-styrene (ABS) copolymer. Small amounts (e.g., up to about 10 wt %) of additional comonomer, such as methyl methacrylate, ethylacrylate, alpha-methylstyrene, vinyltoluene, acrylonitrile, or the like, may be included in the manufacture of some types of ABS. Details concerning PC/ABS blends, their preparation, and their uses can be found in the literature. See for example, R. Greco and A. Sorrentino, Adv. Polym. Technol., 1994, 13(4), 249-258, and references cited therein, and D. W. Jin, K. H. Shon, H. M. Jeong and B. K. Kim, J. Appl. Polym. Sci., 1998, 69(3), 533-542, which journal articles and cited references are incorporated herein by reference as if fully set forth herein.
The polymer compositions of this invention can be in the form of the molded or extruded shape or object itself. Also, the polymer compositions of this invention can be in the form of a masterbatch or concentrated preblend in which the concentration of the flame retardant components therein is higher than the intended concentration in the ultimate finished molded shape or object to be fabricated. Such masterbatch or concentrated preblend is mixed or blended with additional polymer either as dry materials or as a melt blend which is then molded or extruded to produce the finished shape or object.
The flame retarded PC/ABS polymer compositions can constitute finished polymer compositions containing a flame retardant amount of the flame retardants of this invention in the range of about 5 to about 30 weight percent, although it is more desirable in most cases that this upper amount be about 25 weight percent (so that the composition contains a flame retardant amount in the range of about 5 to about 25 weight percent), and even more desirable in most cases that this upper amount be about 20 weight percent (so that the composition contains a flame retardant amount in the range of about 5 to about 20 weight percent). Such weight percentages are based on the weight of the PC/ABS polymer plus the weight of the phosphoramidate flame retardant(s) used therein pursuant to this invention. The weight of other components, if any, used in forming the finished polymer composition is excluded from such calculation. As noted above, one way of forming such polymer compositions is by use of masterbatch or additive-rich preblend compositions made from the PC/ABS substrate polymer and a higher percentage of the phosphoramidate flame retardant(s) of this invention than the percentage to be included in the ultimate finished product. Such masterbatches or additive-rich preblend compositions will typically be a melt blended masterbatch or a powder preblend made from about 25 to about 95 parts by weight of the phosphoramidate flame retardant(s) per hundred parts by weight of such flame retardant(s) plus the substrate PC/ABS polymer. Such masterbatch and additive-rich preblend compositions, which constitute additional embodiments of this invention, can subsequently be used in forming finished polymer compositions by blending an appropriate amount of the masterbatch or additive-rich preblend with an appropriate amount of the PC/ABS polymer which does not contain the phosphoramidate flame retardant component to thereby produce a blend having the desired end use proportions of the phosphoramidate flame retardant component(s) in whatever form they exist after being blended together.
Typically, and preferably, no halogen-containing additive component is intentionally added to the compositions of this invention. Consequently, the preferred compositions of this invention do not contain halogen except for impurities which may occur therein as a consequence of the materials (solvents, catalysts, etc.), process or process equipment used in their synthesis or manufacture. Typically the additive compositions, e.g., a masterbatch or preblend of the flame retardant components, which can be used in accordance with this invention to prepare the finished polymer compositions of this invention, will contain, if any, no more than about 1000 parts by weight of halogen impurities per million parts by weight (ppmw) of additive composition, and thus the term xe2x80x9chalogen-freexe2x80x9d in connection with such additive compositions means that they contain, if any, no more than about 1000 ppmw of halogen. The finished polymer compositions of this invention will typically contain, if any, no more than about 100 parts by weight of halogen impurities per million parts by weight of the total polymer composition. Therefore, the term xe2x80x9chalogen-freexe2x80x9d as used herein in connection with the finished polymer compositions means that they contain, if any, no more than about 100 ppmw of halogen. Usually they will contain less halogen than this, unless a halogen-containing solvent or a halogen-containing gas is used in preparing the resin produced from a PC/ABS polymer composition of this invention.
Similarly, in preferred embodiments no antimony-containing additive is intentionally added to a composition of this invention. Such preferred compositions are devoid of antimony-containing components except possibly for adventitious trace amounts which possibly may find their way into the polymer blends through contamination of blending equipment by antimony additives such as antimony oxides previously used in such equipment.
A further embodiment of this invention is the method of rendering a thermoplastic PC/ABS polymer flame resistant which comprises incorporating therein the above phosphoramidate flame retardant(s) in an amount such that the resultant polymer composition contains a flame retardant amount of the flame retardants in whatever chemical composition and form such components exist in the resultant polymer composition. As noted above, such polymer composition even when devoid of anti-dripping agent typically will provide test specimens exhibiting at least V-2 rating in the UL-94 test procedure.
It may be possible to incorporate the flame retardants of this invention in the substrate polymer prior to, or during, formation of the polycarbonate or ABS polymer. For example, such components may possibly be added to the monomer(s) or to the polymerization system to be used in forming the polymer. Similarly, it may be possible to add the flame retardants to the polymerization mixture during the course of the polymerization reaction itself. Preferably however, the flame retardants of this invention are added to the thermoplastic polymer after the polymer has been produced. It will also be appreciated that the possibility exists for additions being made in stages, such as prior to and during the polymerization, or prior to and after the polymerization, or during and after the polymerization, or prior to, during and after the polymerization.
Other ingredients such as extrusion aids (e.g., barium stearate or calcium stearate), acid scavengers (e.g., magnesium oxide or tetrasodium pyrophosphate), dyes, pigments, fillers, stabilizers, antioxidants, antistatic agents, reinforcing agents, and the like can be included in the polymer compositions of this invention. One or more anti-dripping agents such as suitable fluoropolymers (e.g., tetrafluoroethylene polymer) are desirably included in the polymer compositions of this invention. The particular materials selected for use in the composition of this invention should not materially affect adversely the properties of the finished polymer composition for its intended utility.
Various known procedures can be used to prepare the blends or formulations constituting the compositions of this invention. For example the components to be incorporated into the finished blend can be blended together in powder form and thereafter molded by extrusion, compression, or injection molding. Likewise the components can be mixed together in a Banbury mixer, a Brabender mixer, a roll mill, a kneader, or other similar mixing device, and then formed into the desired form or configuration such as by extrusion followed by comminution into granules or pellets, or by other known methods.
The compositions of this invention can be utilized in the formation of useful articles of the type normally fabricated by molding or extrusion of conventional flame retarded polymers. Molding and extrusion conditions such as temperatures and pressures are within conventional recommended limits.